Catalysts and processes for the manufacture of lower aliphatic alcohols from syngas

ABSTRACT

There are disclosed catalyst formulations and methods for the preparation of oxygenated lower aliphatic compounds. The methods comprise applying a mixture of carbon monoxide and hydrogen to a catalyst formulation under reaction conditions, wherein the catalyst formulation is a solid which may comprise: an active metal, a mixed metal component comprising one or more of a metal A, a metal B, a metal C, and a promoter. In certain embodiments one or more of the metals and the promoter may be present as compounds. In a first embodiment the catalyst comprises a noble metal and an alkali metal promoter, mixed oxides of cerium, zirconium and molybdenum, and an alkali metal promoter. Carbon monoxide and hydrogen may be reacted in the presence of the catalysts disclosed to produce mixtures enriched in lower aliphatic alcohols and particularly ethanol. Various catalyst preparation methods are disclosed including autoignition and gel-sol methods.

FIELD

The present claims and disclosure relate to novel methods to produceethanol and other lower oxygenated aliphatic compounds from synthesisgas.

BACKGROUND

A number of catalysts are known for the conversion of syngas, a mixtureof carbon monoxide, carbon dioxide and hydrogen, to alcohols. For theproduction of alcohols other than methanol, an obstacle in making theconversion process economically viable is the conversion selectivity ofthe catalyst. Ethanol is a desirable product for use as a fuel additivebut it is not efficiently produced by some of the known catalysts.

A first group of catalysts, the promoted methanol catalysts, usuallycontain copper oxide or zinc and an alkali metal promoter such aspotassium or cesium. These catalysts have high selectivity to methanoland isobutanol and produce very little hydrocarbons. A second class ofcatalysts include copper and cobalt or other Group VIII metals such asiron. They produce primarily mixtures of methanol, ethanol and propanol,but usually also have high selectivity to hydrocarbons. A third class ofcatalysts contains molybdenum sulphide as the main component.Selectivity to methanol can be reduced significantly, but again theselectivity for hydrocarbons is high.

SUMMARY

In one aspect there is disclosed a catalyst with improved selectivity tolower oxygenated aliphatics, particularly alcohols and most particularlyethanol.

In particular embodiments the catalyst may be a solid comprising: (a) anactive metal selected from the group consisting of Pd, Pt, Rh, Os or Ir;(b) a mixed metal component comprising one or more of: (i) a metal Aselected from the group consisting of La, Ce, Sm; and (ii) a metal Bselected from the group consisting of Ti, Zr, Hf; and (c) a promoter,the promoter being selected from the group consisting of of Li, Na, K,Rb, Cs and Fr; the gas comprising a mixture of carbon monoxide andhydrogen that react under the reaction conditions in the presence of thecatalyst formulation to form an oxygenated lower aliphatic compound.

In a further embodiment the mixed metal component comprises both metal Aand metal B.

In a further embodiment the mixed metal component further comprises ametal C selected from the group consisting of Mo, Cr and W.

In a further embodiment, if present: metal A is in the form of a metal Acompound; or metal B is in the form of a metal B compound; or metal C isin the form of a metal C compound; or two or more of metals A, B and Care present in the form of compounds.

In a further embodiment the promoter is present in as a promotercompound.

In a further embodiment the metal C is Mo.

In one embodiment there is disclosed a method for the preparation ofoxygenated lower aliphatic compounds comprising applying a gas to acatalyst formulation under reaction conditions, wherein the catalystformulation may be a solid comprising: (a) an active metal selected fromthe group consisting of Pd, Pt, Rh, Os or Ir; (b) a mixed metalcomponent comprising one or more of: (i) a metal A selected from thegroup consisting of La, Ce, Sm; and (ii) a metal B selected from thegroup consisting of Ti, Zr, Hf; and (c) a promoter, the promoter beingselected from the group consisting of of Li, Na, K, Rb, Cs and Fr; thegas comprising a mixture of carbon monoxide and hydrogen that reactunder the reaction conditions in the presence of the catalystformulation to form an oxygenated lower aliphatic compound.

In a further embodiment the mixed metal component comprises both metal Aand metal B.

In a further embodiment the mixed metal component further comprises ametal C selected from the group consisting of Mo, Cr and W.

In a further embodiment, if present: metal A is in the form of a metal Acompound; or metal B is in the form of a metal B compound; or metal C isin the form of a metal C compound; or two or more of metals A,B and Care present in the form of compounds.

In a further embodiment the promoter is present in as a promotercompound.

In a further embodiment the metal C is Mo.

In some embodiments there is disclosed a method for the preparation ofoxygenated lower aliphatic compounds comprising applying a gas to acatalyst formulation under reaction conditions wherein the catalystformulation comprises: an active metal wherein the active metal is Pd,Pt, Rh, Os or Ir; a mixed metal wherein the mixed metal componentcomprises one or more of: (i) a compound of metal A, the metal A beingselected from the group consisting of La, Ce, Sm; and (ii) a compound ofa metal B, the metal B being selected from the group consisting of Ti,Zr, Hf. The catalyst further comprises a promoter selected from thegroup consisting of compounds of Li, Na, K, Rb, Cs and Fr. The gascomprises a mixture of carbon monoxide and hydrogen that react under thereaction conditions in the presence of the catalyst formulation to forman oxygenated lower aliphatic compound.

In alternative embodiments the mixed metal component of the catalystformulation further comprises two or more of: (i) a compound of a metalA, the metal A being selected from the group consisting of La, Ce, Sm;(ii) a compound of a metal B, the metal B being selected from the groupconsisting of Ti, Zr, Hf; and (ii) a compound of a metal C, the metal Cbeing selected from the group consisting of Mo, Cr and W and thepromoter is selected from the group consisting of compounds of Li, Na,K, Rb, Cs and Fr. In alternative embodiments the mixed metal componentmay include one the compounds of metal A, metal B and metal C.

In further alternative embodiments any one of the compounds of the metalA and metal B is selected from the group consisting of oxides,hydroxides, carbonates and hydroxycarbonates; and the compound of themetal C is selected from the group consisting of oxides, hydroxides,carbonates, hydroxycarbonates, chlorides and fluorides.

In yet further alternative embodiments there is disclosed a method formaking a catalyst formulation comprising an active metal, wherein theactive metal is Pd, Pt, Rh, Os or Ir; a mixed metal component comprisingtwo or more of: (i) a compound of a metal A, the metal A being selectedfrom the group consisting of La, Ce, and Sm; (ii) a compound of a metalB, the metal B being selected from the group consisting of Ti, Zr, andHf; and (iii) a compound of a metal C, the metal C being selected fromthe group consisting of Mo, Cr and W; and a promoter, the promoter beingselected from the group consisting of compounds of Li, Na, K, Rb and Cs.The method comprises mixing powdered oxides, carbonates orhydroxycarbonates of two or more of the metal A, the metal B and themetal C; and impregnating the mixture with a solution of a soluble saltof the active metal.

In still further alternative embodiments there is disclosed a method ofmaking a catalyst formulation comprising: an active metal, the activemetal being selected from the group consisting of Pd, Pt, Rh, Os and Ir;a mixed metal compound, the mixed metal component comprising two or morecomponents selected from: a compound of a metal A, the metal A beingselected from the group consisting of La, Ce, Sm; and a compound of ametal B, the metal B being selected from the group consisting of Ti, Zr,Hf; and a compound of a metal C selected from the group consisting ofMo, Cr and W; a promoter the promoter being selected from the groupconsisting of compounds of Li, Na, K, Rb and Cs. The method comprisesmixing a solution of a soluble salt of at least one of the metal A, themetal B, and the metal C with an alkaline salt of at least one of theothers of the metal A, the metal B and the metal C to form a precipitateand impregnating the precipitate with a solution of a soluble salt ofthe active metal.

In still further alternative embodiments there is disclosed a method ofmaking a catalyst formulation wherein the catalyst formulationcomprises: (a) an active metal, the active metal being selected from thegroup consisting of Pd, Pt, Rh, Os and Ir; (b) a mixed metal component,the mixed metal compound component comprising two or more componentsselected from: (i) a compound of a metal A, the metal A being selectedfrom the group consisting of La, Ce, Sm (ii) a compound of a metal B,the metal B being selected from the group consisting of Ti, Zr, Hf; and(iii) a compound of a metal B selected from the group consisting of Mo,Cr and W; and a promoter, the promoter being selected from the groupconsisting of compounds of Li, Na, K, Rb and Cs. The method comprisesautoigniting a mixture of salts of metal A and metal B, and impregnatingthe resulting preparation with suitable forms of the active metal, themetal C and the promoter.

In still further alternative embodiments there is disclosed a method ofmaking a catalyst comprising: (a) an active metal wherein the activemetal being selected from the group -consisting of Pd, Pt, Rh, Os andIr; (b) a mixed metal compound, the mixed metal compound comprising twoor more components selected from: (i) a compound of a metal A, the metalA being selected from the group consisting of La, Ce, Sm; (ii) acompound of a metal B, the metal B being selected from the groupconsisting of Ti, Zr, Hf; and (iii) a compound of a metal C selectedfrom the group consisting of Mo, Cr and W; and (c) a promoter, thepromoter being selected from the group consisting of compounds of Li,Na, K, Rb and Cs. The method comprises the steps of: (d) mixingsolutions of soluble salts of the metal A and the metal B; (e) gellingthe mixture with an acid; and (f) impregnating the resulting preparationwith the metal C, the active metal and the promoter.

In still further alternative embodiments there is disclosed a method ofmanufacturing lower aliphatic alcohols from a mixture comprising carbonmonoxide and hydrogen, the method comprising reacting the mixture in thepresence of the catalyst formulations disclosed.

In still further alternative embodiments there is disclosed a method forthe preparation of oxygenated lower aliphatic compounds comprisingapplying a gas to a catalyst formulation under reaction conditions,wherein the catalyst formulation comprises: (a) an active metal, theactive metal being Pd, Pt, or Ir; (b) a mixed metal component, the mixedmetal component comprising oxides of Ce, Zr and Mo; and (c) a promoter,the promoter being a compound of Li, Na or K; wherein the applied gascomprises a mixture of carbon monoxide and hydrogen that react under thereaction conditions in the presence of the catalyst formulation to forman oxygenated lower aliphatic compound.

In still further embodiments the lower aliphatic compounds may bealcohols, may be higher alcohols and may be ethanol, propanol orbutanol.

In particular embodiments one or more of metal A, B, metal C, and thepromoter may each be omitted, and may be present in free form or ascompounds.

In a further embodiment there is disclosed a method of making a catalystformulation comprising: (a) an active metal wherein the active metal isPd, Pt, Rh, Os or Ir; (b) a mixed metal component wherein the mixedmetal component comprises two or more of: (i) a metal A compound, themetal A being selected from the group consisting of La, Ce, and Sm; (ii)a metal B compound, the metal B being selected from the group consistingof Ti, Zr, and Hf; and (iii) a metal C compound, the metal C beingselected from the group consisting of Mo, Cr and W; and a promotercompound selected from the group consisting of compounds of Li, Na, K,Rb and Cs; the method comprising: (c) mixing powdered oxides, carbonatesor hydroxycarbonates of two or more of the metal A, the metal B and themetal C; and (d) impregnating the mixture with a solution of a solublesalt of the active metal.

In a further embodiment there is disclosed a method of making a catalystformulation wherein the catalyst formulation comprises: (a) an activemetal, the active metal being selected from the group consisting of Pd,Pt, Rh, Os and Ir; (b) a mixed metal component wherein the mixed metalcomponent comprising two or more components selected from: (i) a metal Acompound, the metal A being selected from the group consisting of La,Ce, Sm; (ii) a metal B compound, the metal B being selected from thegroup consisting of Ti, Zr, Hf; and (iii) a metal C compound, the metalC being selected from the group consisting of Mo, Cr and W; and (c) apromoter compound selected from the group consisting of compounds of Li,Na, K, Rb and Cs; the method comprising mixing a solution of a solublesalt of at least one of the metal A, the metal B, and the metal C; withan alkaline salt of at least one of the others of the metal A, the metalB and the metal C to form a precipitate; and impregnating theprecipitate with a solution of a soluble salt of the active metal.

There is further disclosed a method of making a catalyst formulationwherein the catalyst formulation comprises: (a) an active metal, theactive metal being selected from the group consisting of Pd, Pt, Rh, Osand Ir; (b) a mixed metal component wherein the-mixed metal componentcomprising two or more components selected from: (i) a metal A compound,the metal A being selected from the group consisting of La, Ce, Sm; (ii)a metal B compound, the metal B being selected from the group consistingof Ti, Zr, Hf; and (iii) a metal B compound selected from the groupconsisting of Mo, Cr and W; and (c) a promoter compound selected fromthe group consisting of compounds of Li, Na, K, Rb and Cs the methodcomprising autoigniting a mixture of salts of metal A and metal B, andimpregnating the resulting preparation with suitable forms of the activemetal, the metal C and the promoter.

There is further disclosed a method of making a catalyst formulationwherein the catalyst formulation comprises: (a) an active metal, theactive metal being selected from the group consisting of Pd, Pt, Rh, Osand Ir; (b) a mixed metal compound wherein the mixed metal componentcomprising two or more components selected from: (i) a metal A compound,the metal A being selected from the group consisting of La, Ce, Sm; (ii)a metal B compound, the metal B being selected from the group consistingof Ti, Zr, Hf; and (iii) a metal C compound selected from the groupconsisting of Mo, Cr and W and (c) a promoter compound selected from thegroup consisting of compounds of Li, Na, K, Rb and Cs; the methodcomprising the steps of: mixing solutions of soluble salts of the metalA and the metal B; gelling the mixture with an acid; and impregnatingthe resulting preparation with the metal C, the active metal and thepromoter.

In further embodiments there is disclosed the catalyst formulation madeaccording to any one of the methods described.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There are disclosed catalyst formulations, methods for their productionand methods of their use for the preparation of mixtures comprisingoxygenated lower aliphatic compounds starting from gaseous mixturescomprising carbon monoxide and hydrogen. Such mixtures of oxygenatedlower aliphatic compounds may for example comprise alcohols andparticularly may contain ethanol as a predominant product.

In this application “lower aliphatics”, means aliphatic compoundscontaining one or more carbon atom and includes but is not limited toforms containing 1,2,3,4,5,6,7, 8 or more carbon atoms. Oxygenated loweraliphatics includes but is not limited to alcohols, aldehydes, ketones,carboxylic acids and the like.

In this application, “higher alcohols” means alcohols whose moleculescontain two or more carbon atoms. It includes ethanol, propanol,butanol, pentanol, hexanol and other alcohols having two or more carbonatoms in their structure.

Composition of the Catalyst Formulation

Catalysts are described that contain an active metal, a mixed metalcomponent and a promoter. The mixed metal component may comprise one ormore of two metals, A and B, or may comprise both of metal A and B, ortwo or more of each of three metals A, B and C. The metals and promotermay be present in free form or as compounds.

In some embodiments the active metal may for example be chosen from theGroup VIII metals to the right of and including Ni, Rh and Os in thePeriodic Table, such as Pt, Pd and Ir. In specific embodiments, one ormore of Pt, Pd and Ir may be used and in particular embodiments Pd maybe used.

In some embodiments metal A may be La, Ce or Sm, and Ce is used inselected embodiments. In alternative embodiments metal A may for examplebe selected from one or more of Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,Tm, Yb, Lu, Th, Pa, U, Np, Py, Am, Cm, Bk, Cf; Es, Fm, Md, No, Lr or anyrare earth metal with an atomic number between 57 and 70.

In some embodiments metal B may be selected from the group IV-B elementsincluding but not limited to Ti, Zr, Hf, Rf, and Ce. In particularembodiments the preferred metal B is Ti, Zr and Hf and in someembodiments metal B is Zr. It will be understood that where metal A isCe, metal B will not be Ce, and vice versa.

In some embodiments metal C may be selected from metals in group VI-B inthe periodic table, including but not limited to Cr, Mo, W, Sg Nd and U.In certain embodiments metal B is Cr, Mo or W and in specificembodiments Mo is selected. It has been found that in particularembodiments where the metal C is Mo, it may be desirable to excludemolybdenum sulphides from the composition as their presence mayadversely affect the catalyst properties. In some embodiments it maytherefore be desirable though not necessarily essential that the free orcombined form of metal C be partly, be mostly or exclusively at thesurface of the catalyst composition.

The promoter may be selected from free form or compounds of one or moreof the alkali metals, including Li, Na, K, Rb, Cs and Fr. Although thesome alkaline earth metals may also be useable as promoters, it has beenobserved that forms or compounds of the alkaline earth metals maypromote the production of methanol and decrease ethanol selectivityunder some circumstances. In embodiments where alkaline earth metals arenot used as a component of the promoter, it may therefore be desirableto exclude them completely or substantially, substantial exclusion beingunderstood to mean that in different embodiments the amount of alkalineearth metal in free compound form will fall below 1.0% of the totalcatalyst formulation, and in particular embodiments the alkaline earthmetal may comprise, for example 0.5% to 1.0%,0.1% to 0.5%, 0.4% to 0.5%,0.3% to 0.4%, 0.2% to 0.3%, 0.1% to 0.2%, 0.05% to 0.1%, 0.1%, to 0.5%,or 0.0% to 0.1% of the catalyst formulation.

Metals A, B and C and the promoter may be used in combined form, ascompounds. A range of alternative compounds may be suitable for use invarious embodiments. Possibilities include but are not limited tooxides, hydroxides, nitrides, carbonates, hydroxycarbonates, carbides,phosphides , halides, borides, salicylides, oxyhalides, carboxylatessuch as acetates, acetyl acetonates, oxalates, carbonyls and the like.Currently the chosen compounds are generally oxides. It will beappreciated that these compounds may be found in the freshly preparedcatalyst but that when any preparation of the catalyst is in use or hasbeen exposed to reaction conditions, a range of intermediate formscomprising one or more of carbides, phosphides, oxides and nitrides maybe present.

The gas to be applied to the catalyst formulation may be derived from avariety of sources including but not limited to biomass gas, synthesisgas or syngas, landfill gas, stranded gas, natural gas, gas produced bythe partial combustion of hydrocarbons, gas produced by gasification ofhydrocarbonaceous material, gas produced by steam reforming of liquid orgaseous hydrocarbons or any combination of these. All that is necessaryis that the gas contains carbon-monoxide and hydrogen. For optimalperformance and to prolong the life of the catalyst formulation, theapplied gas may be cleared of catalyst inhibitors such as sulphides,halides, nitrogen oxides and sulphur oxides before application to thecatalyst.

In some embodiments the molar ratio of the metal component of thepromoter to the metal B may for example be any value between 0.01 and1.5 but and in particular embodiments may fall between 0.1 and 1.0. Incertain embodiments the ratio of promoter metal to metal B is between0.1 and 0.5. Ratios of 0.01-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.4, 0.4-0.5,0.5-0.6, 0.6-0.7, 0.7-0.8, 0.8-0.9, 0.9-1.0 and above 1.0 are allpossible in specific embodiments. It has been found that under somecircumstances increased promoter content may improve the selectivity forethanol.

In some embodiments the catalyst may have a surface area of betweenapproximately 1 m²/g and 2,000 m²/g and in some embodiments, below 600m²/g; in some embodiments the surface area may have a value of between 2m²/g and 200 m²/g. Ranges of 1-50 m²/g, 50-100 m²/g, 100-200 m²/g,200-300 m²/g, 300-400 m²/g, 400-500 m²/g, 500-600 m²/g, 700-800 m²/g,800-900 m²/g, 900-1000 m²/g, or in excess of 1000 m²/g are all possiblein specific embodiments.

In some embodiments the active metal may make up any value or rangebetween 0.01% and 20% of the weight of the catalyst. In some embodimentsthe active metal makes up between 0.01% and 10% of the catalyst and inspecific embodiments the active metal makes up approximately 0.05% ofthe catalyst. Nonetheless, amounts of below 0.01%, 0.01-05%, 0.05-0.1%,0.1-0.2%, 0.2-0.5%, 0.5-0.75%, 0.75-1.0%, 1.0-2.0%, 2.0-5%, 5.0-10%,10%-12.5%, 1.5%-15%, 15%-17.5%, 17.5-20% and above 20% may all beappropriate, desirable or useable under certain circumstances and incertain embodiments. In some embodiments the active metal may bedeposited partly, mostly or exclusively at surface of the catalystformulation.

Although a range of possible values for the reaction parameters aregiven below, in some embodiments reactions are carried out at atemperature value or range of between 250° C. and 450° C., at apressure. value or range of between 20 and 350 atm, and at a flow ratevalue or range of between 1,000 and 20,000 h⁻¹. The gas may be appliedto the catalyst formulation at a range of temperatures including but notlimited to temperatures anywhere between 50 and 2000° C. In someembodiments the range is 100-600 C and in one embodiment the temperaturerange is between 250° C. and 450° C. It will be appreciated thattemperatures of less than 50° C., from 50-100° C., 100-150° C., 150-250°C., 250-350° C., 350-450° C., 450-550° C., 550-650° C., 650-750° C.,750-850° C., 850-950° C., 950-1050° C, 1050-1200° C., 1200-1400° C.,1400-1600° C., 1600-1800° C., 1800-2000° C. or above 2000° C. may bedesirable under given conditions and may be used in specificembodiments. However, it is generally understood that under normalcircumstances and in certain embodiments, maintaining a temperature ofat least 200° C. may avoid the formation of volatile metal carbonyls andthe consequent accelerated degradation of the catalyst

The gas may be applied to the catalyst formulations under a range ofpressure conditions, including a value or range of pressure of between0.5 atm and 700 atm. Although a pressure anywhere from 20-300 atm isused in some embodiments, pressure ranges of 0.69-14 atm, 14-21 atm,21-70 atm, 70-140 atm, 140-210 atm, 210-280 atm, 280-350 atm, 350-420atm, 420-490 atm, 490-560 atm, 560-630 atm, 630-700 atm, or above 700atm are all possible and may be used in specific embodiments.

In different embodiments, gas may be applied to the catalyst formulationat flow rates of between 100 h⁻¹ and 10,000 h⁻¹. In some embodimentsflow rates of between 1000 h⁻¹ and 6000 h⁻¹ may be suitable and inspecific embodiments flow rates of from 4000-6000 h⁻¹ may be used.Nonetheless, flowrates of 100-1,000 h⁻¹, 1,000-2,000 h⁻¹, 2,000-3,000h⁻¹, 3,000-4,000 h⁻¹, 4,000-5,000 h⁻¹, 5,000-6,000 h⁻¹, 7,000-8,000 h⁻¹,8,000-9,000 h⁻¹, 9,000-10,000 h⁻¹, 10,000-15,000 h⁻¹ or greater may allbe adopted in particular embodiments, with suitable adjustments to thereaction method. Although a range of flow rates is possible, in someembodiments it has been found that substantially lower flow rates mayreduce the ethanol yield from the reaction, as illustrated in theexamples presented below.

In different embodiments, the ratio of hydrogen to carbon monoxide inthe applied gas varied between 1:2 and 4:1 and in the examples given theratio was generally 1:1. However, a wide range of ratios may be useable.For instance ratios of below 1:10, from 1:10-1:8, 1:8-1:6, 1:6-1:4,1:4-1:2, 1:2-1:1, 1:1-2:1, 2:1-3:1, 3:1-4:1, 4:1-5:1, 5:1-6:1, 6:1-7:1,7:1-8:1, 8:1-9:1, and above 9:1 may all be suitable or useable in someembodiments under suitable conditions.

It will be apparent that the different embodiments have differentproperties, including different lower aliphatic alcohols selectivities,different conversion efficiencies and different hydrocarbonselectivities. Some specific parameter values, choices of metals ormetal compound, and combinations of the disclosed components may beundesirable or unsuitable under particular circumstances.

Using the methods and catalysts described herein, the applied gas may bereacted to generate a mixture containing lower oxygenated aliphaticcompounds, particularly alcohols and most particularly ethanol. It willbe appreciated that cyclic compounds, ketones, aldehydes, carboxylicacids, other alcohols and other types of oxygenated compound may equallybe produced. The product mixture may contain a high proportion ofalcohols and in particular may contain a high proportion of ethanol inpreference to methanol or the other lower aliphatic alcohols that may beproduced. In some embodiments the ratio of ethanol to methanol in theproduct mixture may exceed 7 to 3. In alternative embodiments theproduct mixture may comprise more than 50%, more than 60%, more than70%, more than 80% or more than 90% ethanol. Ethanol contents of10%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, 80%-90 or over 90%may be obtainable with different embodiments, depending on thecomposition of the catalyst formulation, the reaction conditions and thecomposition of the applied gas.

In certain embodiments and under suitable conditions the values orranges of the selectivity for the conversion of carbon monoxide tooxygenated lower aliphatic products, and for ethanol in particular, maybe 10%-20%, 20%-30%, 30%-40%, 40%-50%, 50%-60%, 60%-70%, 70%-80%, an inparticular embodiments may be in excess of 80%. Herein selectivity meansthe number of carbon atoms appearing in the product in question, dividedby the number of carbon monoxide molecules converted to all productsother than carbon dioxide. By selectivity for alcohols is meant thetotal number of carbon atoms appearing in the alcohol or alcohols inquestion divided by the total carbon atoms appearing in all products(oxgenated or otherwise) other than carbon dioxide.

In particular embodiments the catalyst formulation may be held on asupport which support may have a surface area of between 50 and 1000m²/g or greater than 1000 m²/g. In some embodiments the support has asurface area of between 100 and 800 m²/g and in some specificembodiments it has a surface area between 100 and 500m²/g. A range ofsurface areas such as 50-200 m²/g, 200-400 m²/g, 400-600 m²/g, 600-800m²/g, 800-1,000 m²/g or more may all be used, in particular embodiments,though the properties of the particular catalyst preparation may beaffected thereby. Possible support materials may include aluminas, basicoxides, silicas, carbon, solid compounds of:magnesium, calcium,strontium, barium, scandium, yttrium, lanthanum, the rare earths,titanium, zirconium, hafnium, vanadium, niobium, tantalum, thorium,uranium and zinc. Oxides are one example of suitable solids but numerousother alternatives may be useable for example: in particular embodimentscarbon, ploymers, zeolites, molecular sieves or combinations thereof maybe used. The supports are preferably neutral or basic or may be made soby the addition of alkaline promoter. The alumina supports include thealpha, gamma and beta types and the silicas include but are not limitedto silica gel, diatomaceous earth, and crystalline silicates. Thesupport may also comprise one or more of the components of the catalystformulation itself, namely the active metal, the promoter compound andthe compounds of metals A, B and C.

In certain embodiments the selectivity for the conversion of carbonmonoxide to hydrocarbons may be less than 20%, less than 10%, may befrom 5-10%, may be less than 5%, less than 3%, or as low as 1% or less.Particular embodiments may yield ethanol at a rate of 20-40, 40-50,50-60, 60-80 or more than 80 grams of ethanol per kg of catalyst perhour.

It will be apparent from the examples that follow that under somecircumstances one or more of the components of the catalyst compositionmay be dispensed with and still yield a functional, though possiblysub-optimal, catalyst.

Preparation of the Catalyst Formulation

A number of methods are disclosed for the preparation of the catalyst.In exemplified embodiments, catalysts were all dried, calcinated andreduced, prior to use.

Method 1: In a first embodiment of the methods for catalyst preparation,bulk form compounds of two or more of metal A, metal B and metal C weremixed. These compounds were generally oxides but could be selected fromthe full range of possible compounds set out herein and the mixing wasachieved by either mechanically mixing the powders or by coprecipitationof the mixed oxides from solution. After mixing, a water soluble salt ofthe active metal was added and the active metal deposited by adjustingthe pH to a suitable value. Generally carbonates and hydroxides wereused for this purpose but numerous alternatives including but notlimited to urea and bicarbonates may be useable in differentembodiments. The resulting catalyst formulation was then dried andcalcinated by standard methods before the further addition of promoter.The resulting catalyst formulation was then calcinated by standardmethods before being reduced. It will be appreciated that this reductioncan be carried out using a variety of known methods, including but notlimited to:reducing the metal oxide or other reducible form to yield themetal by thermal treatments in hydrogen or diluted hydrogen (which may,in some embodiments, be anywhere from1-10% H₂/N₂). The reduction may beperformed in ammonia or carbon monoxide if the reducible form does notreact with carbon monoxide to form carbides with a wide range of suchcombination of reagents and conditions being usable in alternativeembodiments. In certain embodiments the reduction may be accomplished bytreating the formulation with hydrogen gas at elevated temperatures,including but not limited to temperature ranges between about 100° C.and 700° C., including temperature ranges of about 200-300° C., about300-400° C., about 400-500° C. about 500-600° C., about 600-700° C.,about 450-550° C. and in particular embodiments the temperature may beabout 500° C.

Method 2: In a second embodiment of the methods for catalystpreparation, a solution of salts of metals A and B was prepared andprecipitated with a salt of metal C having the general formulaM_(a)(C_(b)N_(c))_(d). Generally the salts of metals A and B werenitrates and the metal C salt was Ammonium Molybdate, Ammonium Chromateor Ammonium Tungstate, although suitable equivalents may be useable incertain embodiments. The product was filtered, washed and dried. Thedried powder mixture was impregnated with a solution of a soluble saltof the active metal, which was then precipitated by adjusting the pH.The resulting solid was impregnated with an alkali comprising thepromoter metal and then dried. The product was calcinated and thenreduced as indicated above. In some embodiments the method may resultsin the deposition of the active metal primarily or exclusively at thesurface of the catalyst formulation.

Method 3: In a third method embodiment of the methods for catalystpreparation a wet process known as autoignition or combustion was usedto produce ultrafine ceria-zirconia powders with narrow sizedistribution. The process used an intimate blending among twoconstituents a fuel and an oxidizer. In certain embodiments the fuel maybe amino-acids or acid-alcohols, but in alternative embodiments itmay-be selected from a range of compounds including but not limitedto:amino-alcohols. In some embodiments the oxidizer is a nitrate but inalternative embodiments it may be selected from the range of compoundsincluding but not limited to chlorates, perchlorates, peroxides andpermanganates). The powder characteristics may be dependent on flametemperature generated during combustion, which itself may be dependenton the nature of the fuel and the fuel-to-oxidant ratio. Oxidizercompounds of metal A and metal B were mixed with a fuel, which in someembodiments was aminoacetic acid/glycine in the required molar ratios ina minimum volume of deionized water to obtain aqueous solutions. Thesesolutions were thermally dehydrated to remove the solvent excess,resulting in a viscous liquid, hereafter termed the “precursor”. As soonas the viscous liquid was formed, the temperature was increased to apoint at which point the viscous liquid swelled and autoignited. Thisautoignition resulted in the rapid evolution of a large volume of gasesto produce voluminous powders. The powder was then calcinated usingnormal procedures to remove traces of undecomposed salts. Powderobtained using a fuel deficient precursor may have the highest surfacearea, and the surface area may decrease as the proportional content offuel increases. Associated gas evolution from the autoignition resultsin a highly porous structure of the resulting powder. After beingcalcinated to remove undecomposed salts, the powder was impregnated withthe appropriate quantity of a dissolved salt of metal C, in practicethis salt was normally an ammonium salt, but a range of alternativesincluding at least water or solvent-soluble salts of the metal C, may beused in different embodiments. The resulting mixture is then calcinedaccording to normal procedures to generate the metal C salt required inthe catalyst (normally an oxide). The calcined mixture may then beimpregnated with a solution of a soluble salts of the active metal, insome embodiments this may be a nitrate but a range of alternatives suchas fluorides, chlorides, bromides, oxides, selenides,organo-compounds:for example acetate can be used in particularalternative embodiments. The dried solid can then be impregnated with asolution of promoter, generally in the form of a hydroxide of thepromoter metal although other compounds such as carbonate, bicarbonates,fluorides, chlorides, bromides, phosphates, nitrates, formates, acetatesmay be used in particular embodiments. Following impregnation theformulation can then be calcined using normal procedures to generate aformulation comprising the promoter.

Method 4: A fourth embodiment of the methods for catalyst preparation isa modified sol-gel method in which the gel is produced by dissolving inwater in the presence of an organic complexing agent, soluble compoundsof the metal or metals. Ultrafine complex oxide of metals A and B wasprepared by a modified sol-gel method. Solutions of soluble salts ofmetals A and B, are prepared in the appropriate metallic ratio. Thesalts may be prepared separately and then mixed in the appropriateratio. In some embodiments such salts may be nitrates but in alternativeembodiments they may be, without selected from at least thefollowing:metal-alkoxids, flourides, bromides, chlorides, phosphates. Asolution of a complexing polyfunctional hydroxy-acid or a suitableequivalent may then be added slowly to the mixture under constantstirring. In particular embodiments the acid used is citric acid, but inalternative embodiments a range of hidroxy-acids is useable for thisfunction, including but not limited to acid-alcohols, polyacids,amino-acids, amino-alcohols. The solution was kept in a water bath orother suitable temperature regulating apparatus at an appropriatetemperature until gelation was complete, and then the as-prepared gelswere dried according to standard procedures such as the heating of gelfor the complete removal of the solvent in air or in inert gas. The gelwas then calcined to obtain a solid solution. The solid-solution wasthen impregnated with a salt of metal C. In some embodiments this was anammonium salt but alternatives used in different embodiments include butare not limited to:water or solvent-soluble salts of the metal C. Theproduct was calcined according to standard procedures, and the activemetal component and promoter component both added as described in Method3 above.

Method 5: In certain embodiments, some catalysts have been prepared by“incipient wetness” or “dry” impregnation technique of the requiredmetals onto supports such as alumina, silica, zeolites, and molecularsieves. According to this procedure the volume of the solutioncontaining the precursor does not exceed the pore volume of the support.A solution containing a mixture of cerium nitrate and zirconyl nitratewas prepared and used to impregnate silica gel. The impregnated silicagel was dried and calcined for 4 hours at 500° C. and then impregnatedwith a solution of ammonium heptamolybdate. The solid was dried at 150°C. The resulting Ce/Zr/Mo oxides comprised 40% by weight of theimpregnated silica, and filled 10% of the pore volume. This material wasimpregnated with Pd(NO₃), calcined at 500° C. and promoted with analkali metal (K or Cs).

Specific examples of the above preparative methods are presented below.It will be noted that many other ways of drying, calcinating andreducing the catalyst formulation are possible. Possible drying methodsinclude but are not limited to heating, heating a solid in an oven at atemperature above 100° C., or rinsing a solid with ethanol to remove thewater, or adding a dehydrating agent, such as NaSO₄, to an organicliquid to remove the water. Calcination is carried out by driving outwater and volatile constituents from a solid by heating. Possiblereducing methods include but are not limited to reduction in ammonia orcarbon monoxide if the reducible form does not react with carbonmonoxide to form carbides.

Reaction Method

In the examples given below, the prepared catalyst formulation wasexposed to syngas at elevated temperature and pressure. Thehydrogen/carbon monoxide ratio in the input syngas varied from about 1/2to 4/1. The operating temperature range was between 200 and 350□C andthe pressure range between 500 and 3000 psig.

EXAMPLES

The following examples illustrate specific combinations of componentsand reaction conditions and serve to illustrate, not to limit, the scopeof the invention. In each of the following examples, unless otherwisespecified, each catalyst composition was tested with a feed gascontaining a 1:1 ratio of hydrogen to carbon monoxide

Example 1

A first catalyst comprised palladium, zirconium oxide, cerium oxide, andlithium oxide

In this example and the other examples that follow, the catalysts wereall prepared in a similar manner unless otherwise indicated. Thecatalyst was prepared by precipitation-deposition. The support was madefrom a mechanical mixture of the pure metal oxides or by precipitationof them from soluble salts. Oxide samples were prepared by grinding themixture of pure oxides with a mortar and pestle for 30-40 min. The driedpowder mixture was impregnated with a solution of Pd (NO₃)₂ in HNO₃ orwith IrCl₃ in water. A solution of K₂CO₃ or NH₄OH, was slowly added at70° C. until the pH value of the mixture reached 10. The dispersion wasthen aged at the same temperature for 1 h. The noble metal hydroxideswere precipitated on the surface of support. The resulting solid wasdried at room temperature for 24 hours, then calcinated in air at 500°C. for 4-5 hours. After preparation the catalyst was placed in thereactor and pre-treated in two steps. In the first the catalyst wasdried in nitrogen flow at 400° C. for 1 hour, and then in the secondstep, reduced in a low hydrogen flow rate (max. 45 cc/min) for 10 hours.The temperature was held at 500° C.

The catalyst test procedure consisted oftemperature-programmed-reduction followed by syngas conversion andproduct analysis. The conversion was monitored over a period of about10-12 hours and the product analysis was done using gas chromatographyand mass spectrometry. The behaviour of some variants of this catalystcomposition are illustrated in Table 1: TABLE 1 Alkali promotedPd—CeO₂—ZrO₂ versus Pd—CeO₂ and Pd—ZrO₂ catalysts Yield, Temp Press GHSVSelectivity, c atom % g/kg cat/hr Catalyst H₂/CO K atm h⁻¹ MethanolC₂₊OH Hydrocarbon C₂₊OH Alcohols Pd—CeO₂—Li₂O 1 549 51 45700 90 1 9 144.7 Pd—ZrO₂—Li₂O 1 551 51 45700 72 2 26 2 29.8 Pd—CeO₂—ZrO₂—Li₂O 1 54551 45700 48 10 42 13 38.1

In this comparison the increased higher alcohols (C₂₊OH) selectivityshown with the third row of Table 1 was associated with mixing thecerium oxide and zirconium oxide before adding the palladium. The mixedoxide showed a significant increase in the higher alcohols yieldcompared to the Pd—CeO₂ and Pd—ZrO₂ catalysts used separately.

Example 2

A promoted CeO₂—ZrO₂ catalyst was operated over a range of gas feedflowrates. The catalysts were prepared as in Example 1 except that bothpotassium and lithium were added simultaneously from 1M solutions ofLiOH and KOH. TABLE 2 Alkali promoted Pd—CeO₂—ZrO₂ operated underdifferent GHSV Yield, Temp Press GHSV Selectivity, c atom % g/kg cat/hrCatalyst H₂/CO K atm h⁻¹ Methanol C₂₊OH Hydrocarbon C₂₊OH AlcoholsPd—CeO₂—ZrO₂—K₂O—Li₂O 1 548 68 45700 27 10 63 12.1 39.2Pd—CeO₂—ZrO₂—K₂O—Li₂O 1 549 68 15100 42 18 40 8.1 14.6Pd—CeO₂—ZrO₂—K₂O—Li₂O 1 549 68 5700 50 22 38 3.2 6.7

Example 3

In this example the alkali promoted CeO₂—ZrO₂ catalyst was furtherpromoted by the addition of molybdenum oxide. The Pd/MoO,/CeO₂—ZrO₂catalyst was prepared by a deposition-precipitation method. A mixture ofZrO₂, CeO₂ and MoO₃ was dispersed in a solution of Pd(NO₃)₂.Subsequently, a 0.25 M Na₂CO₃ solution was slowly added to this solutionat 70° C. until the pH reached 10. The dispersion was then aged at thesame temperature for 1 hour. The resulting solid was filtered and washedwith distilled water, dried for 24 hours at room temperature, and thencalcined at 400° C. for 1 hour in air. The product was impregnated with1M KOH. The molar ratio between Pd and K was 0.4. The calcined catalystwas reduced in two steps:initially a flow of N₂ (396 cc/min) and H₂(40.8cc/min) was passed over the catalyst for 1 hour at 400° C. andsubsequently pure H₂(40.8 cc/min) was passed over the catalyst for 12hours at 500° C.

The results of using this example of the catalyst are set out in Table3. As will be seen, adding molybdenum oxide to the Pd—CeO₂—ZrO₂—Kcatalyst can result and increased selectivity to higher alcohols. As aresult the higher alcohols:methanol ratio in the product may under somecircumstances be significantly greater than one. TABLE 3 Alkali promotedPd—CeO₂—ZrO₂ modified by the addition of molybdenum oxide. Yield, TempPress GHSV Selectivity, c atom % g/kg cat/hr Catalyst H₂/CO K atm h⁻¹Methanol C₂₊OH Hydrocarbon C₂₊OH Alcohols Pd—CeO₂—ZrO₂—K₂O— 1 548 685550 62 14 24 5.4 10.5 Pd—MoO_(x)—CeO₂—ZrO₂—K₂O 1 549 68 5665 19 60 2110 19.6

Example 4

In this example, a Group VIII transition metal to the right of Ni, Rhand Os in the Periodic Table is used as a catalyst for higher alcoholssynthesis when dispersed on neutral mixed metal oxides. It was foundthat Pd can be replaced by other metals including Group VIII metals thatadsorb CO non-dissociatively, in this case Ir. In both cases (Ir and Pd)the catalysts had the same composition with a metal loading of 1 wt %.

A new method of preparation for the multimetallic catalyst support wasused in this example. A solution of Ce(NO₃)₃ 6H₂O was mixed with asolution of ZrO(NO₃)₂ nH₂O. The support precursor was precipitated fromnitrates solution by adding stepwise ammonium heptamolybdate. Thetemperature of reaction was 90° C., the pH ranged from 4 to 5.5. The hotproduct was filtered, washed with distilled water and dried in an ovenfor 12 hours, at 110° C. The dried powder mixture was impregnated with adiluted solution of Pd (NO₃)₂ in HNO₃. A solution of K₂CO₃ was slowlyadded at 70° C. until the pH value of the mixture reached 10. Thedispersion was then aged at the same temperature for 1 h. The Pdhydroxide was precipitated on the surface of the support.

The resulting solid was impregnated with 1M KOH solution and then driedat room temperature for 24 hours. The product was calcinated at 600° C.to obtain a crystalline structure of the catalyst.

The results of tests using these catalyst formulations are shown inTable 4. The data show that Ir is a suitable catalyst for selectiveethanol synthesis. In this example the Ir is dispersed on the neutral,mixed metal oxides. The higher alcohols yield obtained using Ir catalystwas about 35% greater than that obtained with the Pd catalyst. TABLE 4Alkali promoted Pd—MoO_(x)—CeO₂—ZrO₂ versus Ir—MoO_(x)—CeO₂—ZrO₂catalysts Yield, Catalyst and Composn Temp Press GHSV Selectivity, Catom % g/kg cat/hr atomic ratio H₂/CO K atm h⁻¹ Methanol C₂₊OHHydrocarbon C₂₊OH Alcohols Pd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 1 548 685480 47 49 4 18 36 Ir_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5517 29 5417 24.5 40.5

Example 5

The catalyst of this example uses Pd dispsersed on a neutral mixed metaloxide comprising of molybdenum and cerium oxides and a transition metaloxide from group IV-B (Ti or Zr). Table 5 shows the results of using thecompositions of this example. The data show that when Ti replaces Zr,the higher alcohols selectivity decreases significantly, although thehydrocarbon selectivity increases. The formulation was highly selectivefor alcohols synthesis, although the ethanol fraction of the totalalcohols was relatively low. TABLE 5 Alkali promotedPd—MoO_(x)—CeO₂—ZrO₂ versus Pd—MoO_(x)—CeO₂—TiO₂ catalysts Yield,Catalyst and Composn Temp Press GHSV Selectivity, C atom % g/kg cat/hratomic ratio H₂/CO K atm h⁻¹ Methanol C₂₊OH Hydrocarbon C₂₊OH AlcoholsPd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5480 19 60 21 10 19.6Pd_(0.002)Mo_(0.7)Ce₁Ti₁K_(0.29) 1 548 68 5458 27 7 67 2 8.8

Example 6

This example demonstrates the use of Pd dispsersed on a neutral mixedmetal oxide comprising of Zr and Ce oxides and a transition metal oxidefrom group VI-B (Cr,Mo,W). The results of using the compositions of thisexample ate shown in Table 6. The data show that metal oxides chosenfrom Group VI-B all produce some ethanol, but only the formulationscontaining Mo have ethanol selectivities greater than methanol while atthe same time maintaining low hydrocarbon selectivity. TABLE 6 Alkalipromoted Pd—MoO_(x)—CeO₂—ZrO₂, Pd—WO_(x)—CeO₂—ZrO₂ andPd—CrO_(x)—CeO₂—ZrO₂ catalysts Yield, Catalyst and Composn Temp PressGHSV Selectivity, C atom % g/kg cat/hr atomic ratio H₂/CO K atm h⁻¹Methanol C₂₊OH Hydrocarbon C₂₊OH AlcoholsPd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5480 19 60 21 10 19.6Pd_(0.002)W_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5533 51 9 40 2 5.2Pd_(0.002)Cr_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5559 29 18 53 5 7.3

Example 7

This example demonstrates the use of Pd—Mo—Ce—Zr—K catalysts preparedwith different Pd loadings. Results are shown in Table 7. TABLE 7 Alkalipromoted Pd—MoO_(x)—CeO₂—ZrO₂ catalysts with varying Pd content. Yield,Catalyst and Composn Pd content Temp Press GHSV Selectivity, C atom %g/kg cat/hr Atomic ratio wt % K atm h⁻¹ Methanol C₂₊OH Hydrocarbon C₂₊OHAlcohols Pd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 1 548 68 5480 19 60 21 10 19.6Pd_(0.01)Mo_(0.7)Ce₁Zr₁K_(0.2) 5 548 68 5906 17 57.4 26.6 17 26.5

The data show that by decreasing the Pd content of the Pd—Mo—Ce—Zr—Kcatalyst, the higher alcohols selectivity decreases and there is a smalldecrease in higher alcohols yield.

Example 8

This example compares the results of three different catalystpreparation methods. Pd—Mo—Ce—Zr—K catalyst, prepared by theprecipitation-deposition onto a mechanical mixture of metal oxides wascompared the same catalyst composition made by an alternative methodwhereby the three mixed oxides (Mo,Ce and Zr) were first prepared byco-precipitation from solution as described in method 2 above and “dry”impregnation onto silica support as described in method 5. The resultsof testing these three formulations are shown in Table 8. TABLE 8 Alkalipromoted Pd—MoO_(x)—CeO₂—ZrO₂ catalysts prepared by three differentmethods. Catalyst and Composn Yield, Preparation method Temp Press GHSVSelectivity, C atom % g/kg cat/hr Atomic ratio K Atm h⁻¹ Methanol C₂₊OHHydrocarbon C₂₊OH Alcohols Pd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 548 68 548019 60 21 10 19.6 Mechanical mixture Pd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 54868 5412 47 49 4 18 36 Precipitation Pd_(0.002)Mo_(0.7)Ce₁Zr₁K_(0.29) 54868 5925 23 75 2 22 42.3 Dry impregnation on silica

The following further examples illustrate the different methods used forthe preparation of the catalyst.

Example 9

The catalyst was prepared by precipitation-deposition. The support wasmade from a mechanical mixture of the pure metal oxides or byprecipitation of them from soluble salts. Multimetallic oxide sampleswere prepared by grinding the mixture of pure oxides with a mortar andpestle for 30-40 min. The dried powder mixture was impregnated with asolution of Pd (NO₃)₂ in HNO₃ or with IrCl₃ in water. A solution ofK₂CO₃ or NH₄OH, was slowly added at 70° C. until the pH value of themixture reached 10. The dispersion was then aged at the same temperaturefor 1 h. The active metal hydroxides were exclusively precipitated onthe surface of support. The resulting solid was dried at roomtemperature for 24 hours, then calcinated in air at 500° C. for 4-5hours. After preparation the catalyst was placed in a reactor andpre-treated in two steps: First the catalyst was dried in nitrogen flowat 400° C. for 1 hour, and then reduced in hydrogen at a low flow rate(max. 45 cc/min) for 10 hours. The temperature was held at 500° C.

Example 10

This method of preparation was used for the PdMoCeZrK catalyst. Asolution of Ce(NO₃)₃.6H₂O was prepared separately and then mixed with asolution of ZrO(NO₃)₂.nH₂O. The support precursor was precipitated fromnitrates solution by adding stepwise ammonium heptamolybdate. Thetemperature of reaction was 90° C., the pH ranged from 4 to 5.5. The hotproduct was filtered, washed with distilled water and dried in an ovenfor 12 hours, at 110° C. The dried powder mixture was impregnated with asolution of Pd (NO₃)₂ in HNO₃. A solution of K₂CO₃ was slowly added at70° C. until the pH value of the mixture reached 10. The dispersion wasthen aged at the same temperature for 1 h. The Pd hydroxide wasexclusively precipitated on the surface of support. The resulting solidwas impregnated with 1M KOH solution and then dried at room temperaturefor 24 hours. The product was calcinated at 600° C. to obtain acrystalline structure of the catalyst.

Example 11

This example describes the use of autoignition or combustion to produceultrafine ceria-zirconia powders with narrow size distribution. Theprocess used an intimate blending among the constituents:the fuel (whichmay be amino-acids; acids-alcohols etc.) and an oxidizer (such as anitrate). The powder characteristics were dependant on flame temperaturegenerated during combustion, witch itself is dependent on the nature ofthe fuel and the fuel-to-oxidant ratio. In this example, cerium nitrate,zirconium nitrate and aminoacetic acid (glycine) were mixed in therequired m o l a r ratios in a minimum volume of deionized water toobtain aqueous solutions. These solutions, after thermal dehydration (byheating at 1110° C. on a hot plate) to remove the solvent excess,resulted in a viscous liquid, hereafter termed as precursor. As soon asthe viscous liquid was formed, the temperature of the hot plate wasincreased to 200° C. at which point the viscous liquid swelled andautoignited, with the rapid evolution of a large volume of gases toproduce voluminous powders. Because the time for which the autoignitionexists is rather small (<5 sec.), the powder was calcined at 550° C. for1 hour to remove traces of undecomposed glycine and nitrates. Note thatfor glycine-nitrate combustion, a glycine-to-oxidant ratio <0.56 isfuel-deficient and a glycine-to-oxidant ratio >0.56 is a fuel-richratio. The ceria-zirconia powder obtained through the fuel deficientprecursor may have the highest area, and the areas may decrease as theglycine-to-nitrate ratio increases. The minimum amount of fuel used inthe case of the fuel deficient ratio may result in a small reactionenthalpy, and hence, the local temperature of the particles remains low,which may prevent the formation of a dense structure. Associated gasevolution may result in a highly porous structure of the product. Theceria-zirconia powder was impregnated with the appropriate quantity ofammonium heptamolybdate dissolved in water, calcined at 125° C. toobtain MoO₃ and then, impregnated with a solution of Pd(NO₃)₂ in HNO₃.The dried solid was impregnated with KOH and then calcined for 5 hoursat 500° C.

Example 12

A modified sol-gel process was used to make Ce—Zr catalysts. Ceriumnitrate and zirconium nitrate solutions were prepared separately andthen mixed in the appropriate metallic ratio. Citric acid solution wasthen added slowly to the mixture solution under constant stirring. Thesolution was kept in a water bath at 60° C. until the gelation wascomplete, and then the as prepared gels were dried at 120° C. for 24hours. The gel was calcined at 500° C. for 4 hours to obtainceria-zirconia solid solution. The solid was impregnated with ammoniumheptamolybdate, and calcined for 2 hours at 125° C., and thenimpregnated with a solution of Pd(NO₃)₂ in HNO₃. The dried product wasimpregnated with KOH and then calcined at 500° C. for 5 hours.

Although the claimed subject matter has been described in detail andthrough numerous examples, it will be understood that such details areillustrative only and that many variations and modifications can be madewithout departing from the spirit and scope of the subject matterclaimed.

1-29. (canceled)
 30. A method of making a catalyst formulationcomprising: (a) an active metal wherein said active metal is Pd, Pt, Rh,Os or Ir; (b) a mixed metal component wherein said mixed metal componentcomprises two or more of: (i) a metal A compound, said metal A beingselected from the group consisting of La, Ce, and Sm; (ii) a metal Bcompound, said metal B being selected from the group consisting of Ti,Zr, and Hf; and (iii) a metal C compound, said metal C being selectedfrom the group consisting of Mo, Cr and W; and (c) a promoter compoundselected from the group consisting of compounds of Li, Na, K, Rb and Cs;said method comprising (d) mixing powdered oxides, carbonates orhydroxycarbonates of two or more of said metal A, said metal B and saidmetal C; and (e) impregnating said mixture with a solution of a solublesalt of said active metal.
 31. A method of making a catalyst formulationwherein said catalyst formulation comprises: (a) an active metal, saidactive metal being selected from the group consisting of Pd, Pt, Rh, Osand Ir; (b) a mixed metal component wherein said mixed metal componentcomprising two or more components selected from: (i) a metal A compound,said metal A being selected from the group consisting of La, Ce, Sm (ii)a metal B compound, said metal B being selected from the groupconsisting of Ti, Zr, Hf; and (iii) a metal C compound, said metal Cbeing selected from the group consisting of Mo, Cr and W and (c) apromoter compound selected from the group consisting of compounds of Li,Na, K, Rb and Cs said method comprising mixing a solution of a solublesalt of at least one of said metal A, said metal B, and said metal C;with an alkaline salt of at least one of the others of said metal A,said metal B and said metal C to form a precipitate; and impregnatingsaid precipitate with a solution of a soluble salt of said active metal.32. A method of making a catalyst formulation wherein said catalystformulation comprises: (a) an active metal, said active metal beingselected from the group consisting of Pd, Pt, Rh, Os and Ir; (b) a mixedmetal component wherein said mixed metal component comprising two ormore components selected from: (i) a metal A compound, said metal Abeing selected from the group consisting of La, Ce, Sm (ii) a metal Bcompound, said metal B being selected from the group consisting of Ti,Zr, Hf; and (iii) a metal B compound selected from the group consistingof Mo, Cr and W and (c) a promoter compounds selected from the groupconsisting of compounds of Li, Na, K, Rb and Cs said method comprisingautoigniting a mixture of salts of metal A and metal B, and impregnatingthe resulting preparation with suitable forms of said active metal, saidmetal C and said promoter.
 33. A method of making a catalyst formulationwherein said catalyst formulation comprising: (a) an active metal, saidactive metal being selected from the group consisting of Pd, Pt, Rh, Osand Ir; (b) a mixed metal compound wherein said mixed metal componentcomprising two or more components selected from: (i) a metal A compound,said metal A being selected from the group consisting of La, Ce, Sm (ii)a metal B compound, said metal B being selected from the groupconsisting of Ti, Zr, Hf; and (iii) a metal C compound selected from thegroup consisting of Mo, Cr and W and (c) a promoter compound selectedfrom the group consisting of compounds of Li, Na, K, Rb and Cs saidmethod comprising the steps of: (d) mixing solutions of soluble salts ofsaid metal A and said metal B (e) gelling said mixture with an acid; and(f) impregnating the resulting preparation with said metal C, saidactive metal and said promoter.
 34. The method of any one of claim 30wherein said metal C is Mo.
 35. The method of any one of claim 30wherein said metal A is Ce and said metal B is Zr.
 36. The method of anyone of claim 30 wherein most of said active metal is deposited at thesurface of said catalyst formulation
 37. The method of any one of claim30 further comprising calcining and reducing said catalyst formulation.38. The method of claim 37 wherein said reduction is carried out byexposing said catalyst formulation to a gas comprising hydrogen orcarbon monoxide
 39. The method of any one of claim 30 further comprisingdepositing said catalyst formulation on a support.
 40. The method ofclaim 39 wherein said support is a metal oxide.
 41. The method of claim40 wherein said support has a surface area of between 100 and 500 m²/g.42-46. (canceled)
 47. The catalyst formulation made according to any oneof claim 30.